STRUCTURE AND PROPERTIES OF PROTOPLASM 59 



several weeks. In older cells the Protoplasm is greatly obscured by the 

 chlorophyll grains, but young tips may Le found in which it is perfectly clear. 

 With this, as with other materials in which protoplasmic motion exists, the 

 presence of the motion can be taken as evidence that the Protoplasm is in 

 normal condition. Growing in somewhat similar situations, and capable 

 of greenhouse cultivation in the same way, is the Water-weed, Elodea, 

 or Anacharis, canadensis. The plasmodia of slime-moulds, Myxomycetes, 

 may sometimes be found on decaying wood in damp, dark places, and are 

 among the best of materials, especially when made to grow upon slides. 

 Additional practical directions for the examination of these objects, and 

 as well some reference to other good materials, may be found in Chapter 3 of 

 Strasbxjrger's " Handbook of Practical Botany " (translation by Hillhouse, 

 New York, Macmillan Co.). So far as materials for the study of movement 

 are concerned, there is a thorough study of the subject from the present point 

 of view by Grace Bushee in the Botanical Gazette, 46, No. 1, 1908. In this 

 paper a list of available materials, including all of those above mentioned, 

 together with many additional greenhouse plants not heretofore recorded, 

 is given, along with their rates of movement. Among the best materials, in 

 addition to those before mentioned, are the hairs from Abutilon, Tomato, 

 Gloxinia speciosa (especially good), Whitlavia grandiflora, Lobelia Erinus, 

 Heliotrope, and Pelargonium species. 



Demonstration. It is possible to project the Protoplasm upon a screen 

 so as to make its structure (in part), and even its movement, visible to classes 

 of considerable size; but this requires a fortunate combination of project- 

 ing microscope, excellent material (preferably Nitella), and careful prelimi- 

 nary preparation. Some directions therefor are given by Pfeffer in his 

 paper earlier cited (p. 23, note). 



Of the various features displayed by the living Protoplasm 

 studied under the preceding observations, the most striking 

 is its movement, called Streaming. So remarkable and appar- 

 ently characteristic is it that it calls for more exact study, which 

 involves the following inquiry: 



What is the character of the streaming in living Protoplasm, 

 as to amount of the Protoplasm involved, constancy of path and 

 direction, place of greatest activity, and rate under normal condi- 

 tions? 



This requires accurate microscopical study, with the three-dimen- 

 sional nature of the movement in mind, together with microscopical 

 measurements. 



Observation. Select the most actively streaming of the available 

 materials in the foregoing list, preferably Nitella and Tradescantia, 

 mount them in water for the microscope, and determine the observable 

 facts about the movement. Then determine by direct or by micrometer 



